docker-errors-networking

Quick Reference

Rule #1: ALWAYS Use User-Defined Networks

NEVER use the default bridge network. It lacks DNS resolution, proper isolation, and configuration flexibility. ALWAYS create a user-defined bridge network:

docker network create mynet
docker run --network mynet --name web nginx
docker run --network mynet --name api node
# api can reach web via hostname "web" — automatic DNS

Network Debugging Flowchart

Container cannot communicate